A Home-Based Intervention to Improve Adherence to the 24-Hour Movement Guidelines in Young Children: Protocol for a Mobile App–Based Randomized Control Trial

BACKGROUND: One in 10 preschoolers (aged 3-4 y) meet the three 24-hour Movement Guidelines, that is, (1) physical activity, (2) sedentary screen time, and (3) sleep. OBJECTIVE: The overarching aim of this study is to evaluate the effectiveness and feasibility of a 12-week mobile health home-based intervention on 24-hour movement behaviors in preschoolers who meet few guidelines (zero or 1 guideline). METHODS: We will conduct a 12-week randomized controlled trial with a wait-list control in 80 families (40 per arm). Preliminary studies in this population informed intervention app content, features, and app development. Behavior change theories, including transfer theory and the multi-process action control framework, helped inform content presentation and topics. Primary outcomes include device-based and parent-report measures of 24-hour movement behaviors, and the secondary outcome is the feasibility and acceptability of the app. Exploratory outcomes include preschoolers' cognitive and motor skills, changes within the home environment, and behavioral control processes. RESULTS: This 2-phase study (K99/R00) received initial funding in March 2022, and preliminary studies were concluded in December 2023. The main grant received institutional review board approval in April 2024, and the grant funding began in May 2024. The study was registered in Clinical Trials in October 2024 and enrolled its first participant in January 2025. As of October 2025, the study has enrolled 39 families. We anticipate the trial will be completed in late 2026. CONCLUSIONS: This research is designed to test a novel approach to improve all three 24-hour movement behaviors in preschoolers in home settings by using a mobile app. Results from this study will have implications for future 24-hour movement interventions, our understanding of improving all 3 behaviors, and ultimately, improvements in preschoolers' health. TRIAL REGISTRATION: Clinicaltrials.gov NCT06667661; https://clinicaltrials.gov/study/NCT06667661. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/75621.